The invention relates to 4-amino-3-arylamino-6-arylpyrazolo[3.4-d]-pyrimidine derivatives, methods for their preparation and their use as antiviral agents, preferably for the treatment of picornavirus infections.
Picornaviruses, particularly entero- and rhinoviruses, are responsible for a broad spectrum of human diseases. More than 60 different human pathogenic serotypes belong to the enteroviruses (Melnick J in: Fields B et al., editors. Virology. Philadelphia: Lippincott-Raven Publishers; 1996, 655-712). Enterovirus, echovirus, coxsackievirus A and B infections are often characterized by nonspecific fever and cause diseases of the upper respiratory system that often cannot be distinguished from rhinovirus infections. The more serious clinical pictures, which can also occur epidemically, comprise hemorrhagic conjunctivitis, herpangina, hand-foot-and-mouth-disease, aseptic meningitis, encephalitis and acute myocarditis. The problem here is that different types of viruses can cause the same symptoms or one virus type can cause totally different clinical pictures. Thanks to the introduction of modern and sensitive methods in virus diagnostics persistent enteroviral RNA and virus proteins could be identified in connection with chronic diseases such as type II diabetes, poliomyositis and most of all chronic myocarditis. Persistent enterovirus infections also occur in patients with agammaglobulinemia and manifest themselves here as persistent enterovirus meningoencephalitis. Dermatomyositis or polymyositis often appeared as accessory symptoms. The rhinoviruses comprise about 100 serotypes. Rhinovirus infections cause more than half of all respiratory diseases of the upper respiratory system in humans (Couch R B in: Fields B M et al., editors: Fields Virology, 3rd edition. Lippincott-Raven, Philadelphia, 1996, 713-35). For a mean period of illness of about 10 days these colds that take mostly a harmless course cause million fold visits to a doctor's and losses of working and school hours. Possible complications that can occur are otitis media, sinusitis, exacerbation of asthma and cystic fibrosis as well as infections of the lower respiratory system mostly in small children, elderly patients and immunosuppressed patients. As a great variety of types exists, a vaccination prophylaxis is not possible at present. Due to the losses of working hours, visits to a doctor's and medicaments combined with these diseases, rhino- and enteroviruses cause enormous expenses every year. Theses virus infections have been treated symptomatically up to now because virus-specific therapeutics are not available (Rotbart H A: Antiviral Res 2002, 53(2), 83-98). Moreover, antibiotics are often prescribed unnecessarily. Therefore, the development of new virostatics is essential.
The results of the intensive search for possible treatments of enterovirus and rhinovirus infections were summarized by Rotbart in 2002 in a general review article (Rotbart H A: Antiviral Res 2002, 53(2), 83-98). For example, ribavirin inhibits a host cell enzyme, the inosin 5′-monophosphate (IMP)-dehydrogenase. By deactivating this key enzyme for the synthesis of purinnucleotides the replication of picornaviruses can be inhibited in vitro and in vivo. Moreover, ribavirin shall be directly built into the genome of polioviruses and thus additionally act as a mutagen for RNA viruses (Crotty S et al.: Nat Med, 2000, 6(12),1375-9). Due to the serious side effects these compounds are not used for treating infections caused by rhino- and enteroviruses.
Specific targets for the inhibition of the viral RNA synthesis are the genome itself, the viral RNA-dependent RNA polymerase and further viral proteins required for the replication complex. For a long time, guanidines, thiosemicarbazones, benzimidazoles, dipyridamoles and flavones have been known as inhibitors of the polymerases of different picornaviruses in the cell culture. Varying degrees of success could be achieved in vivo in this way. Enviroxime derivatives are considered the most promising candidate with a broad anti-enterovirus- and anti-rhinovirus activity. Enviroxime impedes the synthesis of plus-strand RNA by the binding to the virus protein 3A that is required for the formation of RNA intermediates in the virus reproduction (Heinz B A and Vance L M: J Virol, 1995, 69(7), 4189-97). Moderate or no therapeutic effects, a bad pharmacokinetics and unwanted side effects were observed in clinical studies (Miller F D et al.: Antimicrob Agents Chemother, 1985, 27(1), 102-6). Up to now, clinical data of newer derivatives with better bioavailability and tolerance do not exist.
The protease inhibitor AG 7088 has been developed on the basis of the knowledge about the fine structure and function of the viral protease 2C. In the cell culture in the nanomolar concentration range, AG 7088 has an effect against 48 rhinovirus types and coxsackievirus A21, B3, enterovirus 70 and echovirus 11 (Pattick A K et al.: Antimicrobila Agents Chemother, 1999, 43(10), 2444-50). The final data of the clinical studies are not known so far.
Thanks to the clarification of the molecular structure of the viral capsids, the preconditions for a purposeful design of capsid blockers, the “WIN substances”, have been obtained (Diana G D: Curr Med Chem 2003, 2, 1-12). They inhibit the adsorption and/or the uncoating of rhino- and enteroviruses. Some of the WIN substances have a highly specific effect only against individual genera or virus types of the picornaviruses. Other derivatives inhibit the replication both of rhino- and enteroviruses. Arildone, disoxaril and pirodavir belong for example to the WIN substances. These compounds showed very good antiviral effects in the cell culture. A poor solubility (arildone), low bioavailability (arildone and disoxaril), a rapid metabolization and excretion (disoxaril and WIN 54954) as well as side effects, such as skin rash (WIN 54954), made a clinical application impossible. Great hopes were placed in pleconaril, a further capsid inhibitor. Pleconaril has a very good oral bioavailability and after its binding to the hydrophobe pocket in the viruscapsid it inhibits the penetration of rhino-, echo- and coxsackviruses (Pevear D C et al.: Antimicrob Agents Chemother 1999, 43(9), 2109-15; McKinlay M A et al.: Annu Rev Microbiol 1992, 46, 635-54). Therefore, it is potentially effective against a broad spectrum of virus diseases, from the common cold to the viral meningitis or myocarditis. Resistances were observed for rhinoviruses, enterovirus 71 and coxsackievirus B3 (Ledford R M et al.: J Virol 2004, 78(7), 3663-74; Groarke J M et al.: J Infect Dis 1999, 179(6), 1538-41). Clinical studies in children and adults with an enterovirus meningitis (Abzug M J et al.: Pediatr Infect Dis J, 2003, 22, 335-41) and respiratory infections caused by rhinovirus (Hayden F G et al.: Antivir Ther, 2002, 7, 53-65; Hayden F G et al.: Clin Infect Dis, 2003, 36, 1523-32) took a positive course. However, the proven therapeutic effect was not sufficient for the registration of pleconaril (Picovir, Viropharma, USA) as an agent for the treatment of rhinovirus infections in the USA. In March 2002, a corresponding application was refused by the Food and Drug Administration (FDA) because of a too low therapy success with simultaneously observed side effects.
Pyrazolopyrimidines have also been described as CRF antagonists (e.g. EP 674 642 and EP 691 128) that for example inhibit the adenosine kinase (EP 496 617 or U.S. Pat. No. 4,904,666), the xanthine oxigenase (J. Heterocyc. Chem. 19, 1565, 1982) or other enzyme systems (U.S. Pat. Nos. 2,965,643 and 3,600,389).
Thus, the development of highly effective virustatics for the treatment of rhino- and enterovirus diseases continues to be an essential task in antiviral research. The novel compounds should be well tolerated and get over existing resistances, e.g. against pleconaril.